Alterations in cellular and humoral immunity have been described in both uveitis and ocular tumors; the biologic importance of these alterations is unclear. Is reactivity towards ocular antigens important in the pathophysiology of these diseases or is it an epiphenomenon secondary to nonimmunologic alterations of tissue antigens? Circulating immune complexes have been demonstrated in both animal models and human diseases. Preliminary evidence indicates that some uveitis and ocular tumor patients have elevated levels in immune complexes. Currently studies are ongoing to characterize the nature of the antigen and antibodies in these complexes and use the separated antigens to study specific humoral and cell mediated immunity in these diseases.